A vena cava filter is a device inserted into a blood vessel to capture particles in the blood flow. Typically the device is inserted into a major vein to prevent a blood clot from reaching the lungs. Patients who have recently suffered from trauma, have had a heart attack (myocardial infarction), or who have experienced a major surgical procedure (e.g., surgical repair of a fractured hip, etc.) may have thrombosis in a deep vein. When the thrombus clot loosens from the site of formation and travels to the lung it may cause pulmonary embolism, a life-threatening condition. A vena cava filter may be placed in the circulatory system to intercept the thrombi and prevent them from entering the lungs.
Examples of various blood vessel filters are disclosed in U.S. patent application, Publication No. 2001/0000799 A1, titled “BODY VESSEL FILTER” by Wessman et al., published May 3, 2001; U.S. patent application, Publication No. 2002/0138097 A1, titled “ATRAUMATIC ANCHORING AND DISENGAGEMENT MECHANISM FOR PERMANENT IMPLANT DEVICE” by Ostrovsky et al., published Sep. 26, 2002; U.S. patent application, Publication No. 2002/0193828 A1, titled “ENDOVASCULAR FILTER” by Griffin et al., published Dec. 19, 2002; U.S. patent application, Publication No. 2003/0199918 A1, titled “CONVERTIBLE BLOOD CLOT FILTER” by Patel et al., published Oct. 23, 2003; U.S. patent application, Publication No. 2003/0208227 A1, titled “TEMPORARY VASCULAR FILTERS AND METHODS” by Thomas, published Nov. 6, 2003; U.S. patent application, Publication No. 2003/0208253 A1, titled “BLOOD CLOT FILTER” by Beyer et al., published Nov. 6, 2003; U.S. Pat. No. 4,425,908, titled “BLOOD CLOT FILTER” issued to Simon, dated Jan. 17, 1984; U.S. Pat. No. 4,643,184, titled “EMBOLU.S. TRAP” issued to Mobin-Uddin, dated Feb. 17, 1987; U.S. Pat. No. 4,817,600, titled “IMPLANTABLE FILTER” issued to Herms et al., dated Apr. 4, 1989; U.S. Pat. No. 5,059,205, titled “PERCUTANEOU.S. ANTI-MIGRATION VENA CAVA FILTER” issued to El-Nounou et al., dated Oct. 22, 1991; U.S. Pat. No. 5,344,427, entitled “FILTER WITH TRIANGULAR FINGERS” issued to Cottenceau et al., dated Sep. 6, 1994; U.S. Pat. No. 5,626,605, entitled “THROMBOSIS FILTER” issued to Irie et al., dated May 6, 1997; U.S. Pat. No. 5,755,790, titled “INTRALUMINAL MEDICAL DEVICE” issued to Chevillon et al., dated May 26, 1998; U.S. Pat. No. 6,258,026 B1, titled “REMOVABLE EMBOLU.S. BLOOD CLOT FILTER AND FILTER DELIVERY UNIT” issued to Ravenscroft et al., dated Jul. 10, 2001; U.S. Pat. No. 6,443,972 B1, titled “VASCULAR FILTER” issued to Bosman et al., dated Sep. 3, 2002; U.S. Pat. No. 6,497,709 B1, titled “METAL MEDICAL DEVICE” issued to Heath, dated Dec. 24, 2002; U.S. Pat. No. 6,506,205 B2, titled “BLOOD CLOT FILTERING SYSTEM issued to Goldberg et al., dated Jan. 14, 2003; and U.S. Pat. No. 6,517,559 B1, titled “BLOOD FILTER AND METHOD FOR TREATING VASCULAR DISEASE” issued to O'Connell, dated Feb. 11, 2003; U.S. Pat. No. 6,540,767 B1, titled “RECOILABLE THROMBOSIS FILTERING DEVICE AND METHOD” issued to Walak et al., dated Apr. 1, 2003; U.S. Pat. No. 6,620,183 B2, titled “THROMBU.S. FILTER WITH BREAK-AWAY ANCHOR MEMBERS” issued to DiMatteo, dated Sep. 16, 2003; each of which is incorporated herein by reference in its entirety.
Typically the vessel filter comprises a plurality of radially expandable legs that supports one or more filter baskets which are conical in configuration. The device is adapted for compression into a small size to facilitate delivery into a vascular passageway and is subsequently expandable into contact with the inner wall of the vessel. The device may later be retrieved from the deployed site by compressing the radially expanded legs and the associated baskets back into a small size for retrieval. Alternatively, the vessel filter may be configured for permanent implantation. The radially expandable leg may further comprise engagements for anchoring the filter in position within a blood vessel (e.g., vena cava). For example, the expandable legs may have hooks that can penetrate into the vessel wall and positively prevent migration of the filter in either direction along the length of the vessel. The body of the filter may comprise various biocompatible materials including compressible spring metals and shape memory materials to allow easy expansion and compression of the filter within the vessel. The hooks on the radially expandable legs may further comprise materials more elastic than the legs to permit the hooks to straighten in response to withdrawal forces to facilitate withdrawal from the endothelium layer without risk of significant injury to the vessel wall. In one variation, the hooks are formed on the ends of a portion of the radially expandable legs, but not on others.
For treatment of recurrent pulmonary embolism, a vessel filter may be permanently implanted in the patient's vena cava. Alternatively, the vessel filter may be implanted in the patient's vena cava for a few weeks, after which the vessel filter is removed. However, during the implanted period, it is generally difficult to monitor the condition of the vessel filter. For example, to verify that the vessel filter has not migrated along the length of the blood vessel or become misaligned post-implantation, complex imaging systems such as MRI, CT Scan or X-ray may be needed to determine the condition of the vessel filter. In addition, the hooks on the implanted vessel filter may penetrate and/or perforate the blood vessel wall. Perforation of the blood vessel may require immediate intervention by the physician. Furthermore, a possible contraindication associated with the implantation of vessel filter is the build-up of significant amount of trapped thrombus either within the implanted filter or directly upstream from the vessel filter. The built of thrombus may result in complications that require intervention by the physician. For example, when too much thrombus has been trapped inside and/or behind the vessel filter, the build-up may impede blood flow in the blood vessel. The pressure build-up due to the partial blockage of the blood flow may also lead to expansion of the blood vessel, which may cause tilting and/or migration of the vessel filter. In addition, for retrievable filter application, too much thrombus build-up may also make it difficult to compress the vessel filter and thus hinder the vessel filter removal process. In some medical condition, it may also be desirable to wait till the captured thrombus has lysed before the physician proceed with the removal of the vessel filter. Thus, it may be desirable to monitor the position/orientation of the implanted vessel filter and/or the condition/parameter of the implanted vessel filter.
Various vascular devices with built-in sensors have been previously disclosed. Examples of some of these filters are described in U.S. patent application, Publication No. 2003/0171803 A1, titled “ENDOVASCULAR DEVICE FOR ENTRAPMENT OF PARTICULATE MATTER AND METHOD FOR U.S.E” by Shimon, published Sep. 11, 2003; U.S. patent application, Publication No. 2002/0165575 A1, titled “VASCULAR FILTRATION DEVICE” by Saleh, published Nov. 7, 2002; U.S. patent application, Publication No. 2004/0082867 A1, titled “VASCULAR GRAFT WITH INTEGRATED SENSOR” by Esch et al., published Apr. 29, 2004; U.S. Pat. No. 6,652,556, titled “FILTER APPARATU.S. FOR OSTIUM OF LEFT ATRIALAPPENDAGE” issued to VanTassel et al., dated Nov. 25, 2003; U.S. Pat. No. 5,053,008, titled “INTRACARDIAC CATHETER” issued to Bajaj, dated Oct. 1, 1991; U.S. Pat. No. 6,623,507 titled “VASCULAR FILTRATION DEVICE” issued to Saleh, dated Sep. 23, 2003; U.S. Pat. No. 6,702,847 titled “ENDOLUMINAL DEVICE WITH INDICATOR MEMBER FOR REMOTE DETECTION OF ENDOLEAKS AND/OR CHANGES IN DEVICE MORPHOLOGY” issued to DiCarlo, dated Mar. 9, 2004; U.S. Pat. No. 6,053,873 titled “PRESSURE-SENSING STENT” issued to Govari et al., dated Apr. 25, 2000; U.S. Pat. No. 6,092,530 titled “REMOTELY INTERROGATED IMPLANT DEVICE WITH SENSOR FOR DETECTING ACCRETION OF BIOLOGICAL MATTER” issued to Weissman et al., dated Jul. 25, 2000; U.S. Pat. No. 6,206,835 titled “REMOTELY INTERROGATED DIAGNOSTIC IMPLANT DEVICE WITH ELECTRICALLY PASSIVE SENSOR” issued to Spillman et al., dated Mar. 27, 2001; U.S. Pat. No. 6,726,703 titled “DISTAL PROTECTION DEVICE AND METHOD” issued to Broome et al., dated Apr. 27, 2004; each of which is incorporated herein by reference in its entirety. Most of these devices utilize sensors to monitor the physiological condition of the surrounding environment (e.g., blood pressure, temperature, blood chemistry, etc.), and the sensors are not designed to monitor the condition of the device itself.
An improved filter with a mechanism and/or a sensor for monitoring the condition of the implanted vessel filter may be desirable. For example, an electronic circuit that is capable of monitoring a physical parameter of the vessel filter, and thereby notify the user of the condition of the vessel filter may be desirable. A device that can provide efficient and cost-effective verification of the condition of the implanted vessel filter will improve the physicians confidence in the implanted device, and also allow the physician to intervene when the vessel becomes dislodged through migration or when too much thrombus has been captured within the vessel filter. In particular, a device that allows regular monitoring of the vessel filter while the patient is away from the hospital or the treatment facility may be especially useful in preventing occurrences of serious complications while the vessel filter is implanted.